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A195613
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Numbers n with property that n, 2n-1 and 2n+1 are composite.
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0
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25, 28, 32, 38, 46, 58, 60, 62, 72, 77, 80, 85, 88, 92, 93, 94, 102, 104, 108, 110, 118, 122, 123, 124, 130, 133, 143, 144, 145, 148, 150, 152, 160, 161, 162, 164, 170, 171, 172, 178, 182, 185, 188, 196, 202, 203, 206, 207, 208, 212, 213, 214, 218, 226, 235
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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In A000027, if n, n+(n-1) and n+(n+1) are composite, then n is a term of this sequence.
Suggestion: there are arbitrarily long sets of consecutive integers, e.g., 632..637, 665..672, 6428..6443.
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LINKS
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Table of n, a(n) for n=1..55.
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MATHEMATICA
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Select[Range[2, 1000], !PrimeQ[2#-1]&&!PrimeQ[#]&&!PrimeQ[2#+1]&]
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CROSSREFS
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Sequence in context: A015734 A221617 A083806 * A127652 A219258 A044861
Adjacent sequences: A195610 A195611 A195612 * A195614 A195615 A195616
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KEYWORD
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nonn
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AUTHOR
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Zak Seidov, Sep 21 2011
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STATUS
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approved
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